In recent years, in view of savings in resources and conservation of energy, there have been increasing demands for nickel-hydrogen secondary batteries, nickel-cadmium secondary batteries, lithium ion secondary batteries, etc. which can be used repeatedly. Among them, lithium ion secondary batteries are characterized by lightness in weight, high electromotive force, and high energy density. Thus, there are growing demands for the lithium ion secondary batteries as power sources for driving various kinds of mobile electronic devices and portable communication devices such as mobile phones, digital cameras, video cameras, and laptop personal computers.
On the other hand, to reduce used amount of fossil fuel, and to reduce the amount of emission of CO2, expectations for battery packs are growing to serve as power sources for driving motors such as vehicles. Such a battery pack includes a plurality of battery modules each including one or more batteries in order to obtain a preferable voltage and capacity.
In the development of the above battery modules, downsizing the battery modules is a major challenge because the battery modules for storing predetermined electric power are accommodated in limited space, for example, in a vehicle.
For this purpose, a configuration is disclosed in which a battery assembly (a battery module) includes a plurality of batteries, and the connection between the batteries and an interconnect for detecting a voltage, temperature, or the like are implemented by patterned interconnects formed on a printed circuit board (for example, see Patent Document 1). Likewise, a power supply device (a battery pack) is disclosed in which a plurality of power modules are accommodated in a holder case, and is connected to each other by an end plate (for example, see Patent Document 2). The end plate is provided with a sensor lead and a power-supply lead for connecting the battery modules to each other, so that it is possible to reduce connection failures, and downsizing can be possible.
Moreover, as the capacity of a battery to be accommodated in a battery module increases, heat may be generated in the battery itself, and the battery may have a high temperature depending on how it is utilized. Thus, in addition to the safety of the battery itself, the safety of the battery module, which is a collection of batteries, becomes more important. That is, the internal pressure of the battery may be increased by gas generated due to overcharge, overdischarge, or an internal or external short-circuit, and thus the outer case of the battery may rupture. For this reason, generally, a battery is provided with a vent mechanism or a safety valve to release gas so that the gas in the battery is released. Here, when the released gas is, for example, ignited, smoking may occur, or in rare cases, combustion may occur, which poses a problem with reliability and safety.
For this reason, a power supply device (battery module) is disclosed in which a plurality of batteries are accommodated in a battery chamber within a case, and a partitioning wall has openings facing safety valves of the batteries, so that gas emitted from a battery in a fault state is released from an outlet via an exhaust chamber (for example, see Patent Document 3).